700
M. Dohlus et al.
production of defects like point defects in semiconductors is possible. In comparison
to ion beam related defects, radiation damages produced byelectrons are loosely
connected, thus avoiding extended defects.
The electron irradiation of polymers produces a substantial fraction of radicals
(charged or neutral) which react strongly with other polymers, monomers or additional substances. The processing of polymers by electron bombardment fulfills the
demands of modern industrial production e.g. the compatibility with environmental
requirements. This is particularly the case for all processes which include the curing
of adhesive coatings. Furniture, cloth production and paper industries have adopted
electron beam processes. Electron beams of lateral dimensions of 1 m or more
are incorporated into production lines [36]. In many of these processes the need
to remove dangerous fumes can be avoided.
The vulcanization process in the rubber industry proceeds under electron beam
treatment without the addition of sulfur. The applied doses range from 30 to 50 kGy.
For curing of coatings, adhesives, ink on paper, plastic and metal substrates low
energy accelerators (75–300 keV) are used. Such materials consist of oligomers
(acrylated urethane polyesters, acrylated epoxies and polyethers) and monomers
(trimethylolpropane triacrylate) to provide fluidity before curing. The radiation
technique avoids the use of volatile solvents, thus helping to reduce pollution.
Comparatively low doses of less than 50 kGy are used.
High energy accelerators (up to 10 MeV) are used to cure fiber-reinforced
composite materials reducing processing time and the costs. Doses of 150–250 kGy
are needed to obtain a combination of polymerization and crosslinking. These
composite parts are now being used in automobiles and aircrafts.
The insulation of electrical wires as well as the production of jackets on multiconductor cables by radiation crosslinking was one of the first commercial applications. Materials used in this application are, e.g., polyethylene, polyvenylchloride,
ethylene-propylene rubber, polyvenylidene fluoride and ethylene tetrafluoroethylene
copolymer. Besides the creation of radicals, the electron beam can be used to create
defects in crystals. One of the applications is the change or creation of the color of
gemstones e.g. to create fancy diamonds. The electron beam in combination with
a heat treatment changes the diamond color from yellow over green to red. These
modified diamonds must be declared as “treated” to distinguish them from very
rare colored natural diamonds with extreme high worth [37]. In the semiconductor
industry, electron radiation is used to produce defects. These defects induce a
life time reduction of charge carriers and allow a fast switching of electron high
power devices [38]. This procedure is known as life-time killing and became very
important for the production of high power devices e.g. for automotive or energy
industrial products.
Radiation crosslinking stabilizes the initial dimensions of products and imparts
the so-called “memory” effect. If the material is heated the original resistivity is
maintained. Examples of commercial products using this effect are encapsulations
for electronic components or exterior telephone cable connectors.
Low doses (30–50 kGy) of electron beam radiation are applied to automobile
tires before assembling the different components.
M. Dohlus et al.
production of defects like point defects in semiconductors is possible. In comparison
to ion beam related defects, radiation damages produced byelectrons are loosely
connected, thus avoiding extended defects.
The electron irradiation of polymers produces a substantial fraction of radicals
(charged or neutral) which react strongly with other polymers, monomers or additional substances. The processing of polymers by electron bombardment fulfills the
demands of modern industrial production e.g. the compatibility with environmental
requirements. This is particularly the case for all processes which include the curing
of adhesive coatings. Furniture, cloth production and paper industries have adopted
electron beam processes. Electron beams of lateral dimensions of 1 m or more
are incorporated into production lines [36]. In many of these processes the need
to remove dangerous fumes can be avoided.
The vulcanization process in the rubber industry proceeds under electron beam
treatment without the addition of sulfur. The applied doses range from 30 to 50 kGy.
For curing of coatings, adhesives, ink on paper, plastic and metal substrates low
energy accelerators (75–300 keV) are used. Such materials consist of oligomers
(acrylated urethane polyesters, acrylated epoxies and polyethers) and monomers
(trimethylolpropane triacrylate) to provide fluidity before curing. The radiation
technique avoids the use of volatile solvents, thus helping to reduce pollution.
Comparatively low doses of less than 50 kGy are used.
High energy accelerators (up to 10 MeV) are used to cure fiber-reinforced
composite materials reducing processing time and the costs. Doses of 150–250 kGy
are needed to obtain a combination of polymerization and crosslinking. These
composite parts are now being used in automobiles and aircrafts.
The insulation of electrical wires as well as the production of jackets on multiconductor cables by radiation crosslinking was one of the first commercial applications. Materials used in this application are, e.g., polyethylene, polyvenylchloride,
ethylene-propylene rubber, polyvenylidene fluoride and ethylene tetrafluoroethylene
copolymer. Besides the creation of radicals, the electron beam can be used to create
defects in crystals. One of the applications is the change or creation of the color of
gemstones e.g. to create fancy diamonds. The electron beam in combination with
a heat treatment changes the diamond color from yellow over green to red. These
modified diamonds must be declared as “treated” to distinguish them from very
rare colored natural diamonds with extreme high worth [37]. In the semiconductor
industry, electron radiation is used to produce defects. These defects induce a
life time reduction of charge carriers and allow a fast switching of electron high
power devices [38]. This procedure is known as life-time killing and became very
important for the production of high power devices e.g. for automotive or energy
industrial products.
Radiation crosslinking stabilizes the initial dimensions of products and imparts
the so-called “memory” effect. If the material is heated the original resistivity is
maintained. Examples of commercial products using this effect are encapsulations
for electronic components or exterior telephone cable connectors.
Low doses (30–50 kGy) of electron beam radiation are applied to automobile
tires before assembling the different components.